Study under review: Pharmaceutical quantities of yohimbine found in dietary supplements in the USA
Sexual dysfunction is a worldwide issue that generally gets worse with age. It can be highly distressing and may demand expensive solutions, often in the form of powders and pills.
However, many people would rather swap pharmaceuticals for a more "natural" solution. This preference is supported by a steadily growing herbal dietary supplement market in a weak economic environment. Among the twenty best-selling herbal dietary supplements in the U.S. in 2010 was P. johimbe bark extract, also known as yohimbe, which is sold to enhance athletic and sexual performance. Though traditionally used as an aphrodisiac in Africa, no human clinical trials have confirmed its efficacy for this purpose.
Yohimbine, on the other hand (shown in Figure 1), is the most active of the various naturally occurring alkaloids that are found in yohimbe. Unlike yohimbe, yohimbine’s efficacy in treating ED has been examined in multiple clinical trials, and it was once sold as a pharmaceutical drug for this purpose. Yohimbine acts by readily penetrating the central nervous system, resulting in increased norepinephrine release and sympathetic tone, which leads to stimulatory effects and constriction of blood vessels. A review of several well-designed studies suggested that yohimbine is modestly effective in treating ED. Other studies suggest that yohimbine in high doses may lead to adverse side effects, such as hypertension, headaches, and panic attacks, suggesting that yohimbine’s risks may outweigh its benefits. Eventually, yohimbine was removed from the Physician’s Desk Reference, and replaced by drugs like Viagra, which are thought to be safer and more effective.
Yohimbine is still found in over 550 yohimbe brands sold in the U.S., which has caused some concern. It has been linked to 130 hospitalizations between 2000 and 2006 in California alone (based on Poison Control Data) and is banned for sale in Canada, Australia, the Netherlands, and the United Kingdom. There is also some concern that man-made (synthetic) yohimbine may be found in some yohimbe supplements. This is problematic, since it is illegal to include synthetically produced compounds in dietary supplements.
In light of this, the study under review investigated whether supplement brands that were labeled as containing yohimbe, yohimbine or both 1) contained pharmacological doses of yohimbine, 2) disclosed potential adverse side effects, 3) stated accurate quantities of yohimbine on their labels, and 4) contained synthetic yohimbine.
Yohimbe is widely supplemented to treat sexual dysfunction, despite a lack of clinical support. Yohimbine, the primary alkaloid in yohimbe, was originally used as a pharmaceutical to treat ED, but eventually left the drug market due to limited safety and efficacy. It can still be found in a variety of yohimbe dietary supplements in the U.S., which may disclose inaccurate dosages, provide limited safety information, and contain pharmaceutical quantities or synthetic yohimbine, as the study under review explored.
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Other Articles in Issue #12 (October 2015)
Eat less, live more
Animal trials suggest that calorie restriction may extend lifespan. This is the longest human trial conducted thus far on the topic, and serves to inform calorie restriction’s health impacts and feasability.
Am I less hungry after I eats me spinach?
The gut is a hot weight loss topic, even aside from the microbiome -- some pharmaceutical drugs attempt to manipulate hormones or fat digestion in order to spur weight loss. What if an extract of spinach could also impact these factors?
Sugar Wars, Episode 2: “Fructose Strikes Back”
Few food components have been demonized as much as fructose in the past decade. With fructose being presumed guilty in metabolic syndrome and heart disease, this systematic review sheds light on it’s actual impact on blood lipids.
- Interview: Robert Krikorian Ph.D.
Paying attention to omega-3s for ADHD
With more and more people being diagnosed with ADHD, there’s a continuing hunt for helpful treatments. Researchers tested an omega-3 supplement on young males, and also explored a potential dopamine-related mechanism.
- Interview: Trevor Kashey, Ph.D.
From jelly to muscle: collagen and body composition
Collagen has long been equated to junk protein, at least if you’re looking to gain muscle. Could it be underrated for this purpose? A trial of older men tested collagen protein to see if it could boost muscle gain and fat loss.
Throwdown, round 1: plant vs animal protein for metabolic syndrome
The DASH diet is frequently tested in clinical trials, and often performs well. But the diet’s formulation includes strong limitations on red meat, which may be based on outdated evidence. This study compared animal-protein rich diets with a typical DASH diet.
Can omega-3s modulate the mind-muscle connection?
While strength gains are usually associated with protein and muscle-related ergogenics, the nervous system isn’t targeted as often. This study explored a different type of omega-3 source (seal oil) for neuromuscular exercise effects.